1. Technical Field
The present invention relates to a device and a method for generating three mode signals, and more particularly, to a device and a method for generating three mode signals capable of outputting three mode signals using a single input terminal Pin without using a separate external power source, in setting a current mode determining brightness of an LED.
2. Description of the Related Art
An organic light emitting diode (LED) has been prevalently used in various fields such as lighting, a backlight unit (BLU), or the like. Recently, the market for the organic light emitting diode (LED) has expanded quickly and relevant technologies have rapidly developed accordingly.
The miniaturization and lightness of electronic devices has greatly been of interest over the decades. Recently, there has been a need for a function capable of displaying three or more modes by using a single pin while improving functions of a chip.
Meanwhile, the setting and control of the LED current may be determined by a dimming signal (ADIM) and a resistance (RLED) parameter. In order to vary resistance, the resistance should be separately controlled by a variable resistor and should be controlled by replacing a resistor. Depending on the situation, it is difficult to vary current while replacing the resistor. Therefore, in order to represent three or more outputs by using a single pin, a scheme of varying the dimming signal and setting current has been prevalently used.
The related arts are represented by three or more outputs by controlling the above-mentioned dimming signal, which are a single wire control scheme added with a separate digital block, a single wire clock counting scheme, an analog dimming scheme using an analog input, or the like.
In this case, when the digital block is applied, it is possible to represent various levels of outputs. However, as the number of levels is increased, there are problems in that the circuit is complicated and the chip size is increased.
Further, when the analog dimming scheme is applied, it can set various outputs but reflects noise of an input to an output as it is. As a result, since a high-precision and noise-resistant external power source is separately needed, there are problems in that the chip size is increased and the product cost is increased.
FIG. 1 shows a method of setting an LED current using a clock according to the related art.
When a clock signal input to an input terminal is counted in a clock counter and is transferred to a digital analog converter, it is possible to vary a level of an analog transformation dimming voltage corresponding to the number counted in the digital analog converter. The ADIM voltage is generally set in one direction. For example, if it is assumed that a resolution of the ADIM is 1/10 and it is 10 mA per one clock, it is continuously increased from 10 mA→(to?) 20 mA→. . . →100 Ma according to the number of clocks and is reset to 0 mA in a subsequent clock and is again increased from 10 mA according to the clock.
FIG. 2 shows a method of setting an LED current by an external analog dimming method of the related art.
Since the LED current is changed according to a direct input of the ADIM voltage, the LED current is increased or reduced in two directions according to the fluctuation of the external ADIM voltage and the LED current is changed according to the applied voltage without a separate additional circuit since the direct voltage is controlled by the analog signal.
However, as described above, there are problems in that both of the methods need the external power source, make the chip size large, are sensitive to the noise of the input signal, or the like.